Coordinated multi-point (CoMP) technology is an important content in the study of a long-term evolution advanced (LTE-A) scheme of a next-generation wireless communication system, which uses multiple cells for joint transmission, and may enhance a diversity effect, or suppress inter-cell interference, thereby improving the performance of the system.
The current CoMP technology is focused on the field of close-loop (having precoding matrix index (PMI) feedback) transmission, and its transmission technology may include joint processing (JP) and coordination scheduling/beamforming (CS/CB). Following description is given to JP.
FIG. 1 is a schematic diagram of JP transmission taking CoMP between two cells as an example. As shown in FIG. 1, Tx1 and Tx2 denote respectively a base station 1 and a base station 2. A base station here denotes various transmitters capable of CoMP operations, such as an eNB, and a remote radio head (RRH), etc. A base station is configured with Nt transmission antennas, and Rx denotes a user receiver configured with Nr receiving antennas. Multiple input multiple output (MIMO) channel matrices between the base stations 1 and 2 and a user are respectively denoted by H1 and H2, which are Nr×Nt dimension matrices. x denotes L data streams to be transmitting to a user, and the base stations 1 and 2 respectively use Nt×L dimension matrices W1 and W2 to map x to a plurality of antennas of itself for transmission. Wherein, Nr, Nt and L are positive integers, and L≦Nr. A vector symbol received by user equipment may be expressed as y=H1W1x+H2W2x+n, where, n denotes a noise vector.
In order to ensure the performance of CoMP transmission, the user equipment needs to feed back a precoding matrix index (PMI) according to the current channel state, so as to offer proposals to a base station for selecting precoding matrices W1 and W2.
However, in the implementation of the present invention, the inventors found that a defect exists in the above technology: the network end limits the total amount of feedback for the sake of the bearable feedback load; for example, the user equipment is not allowed to feed back at present, or the network end allows feeding back, but the PMI fed back by the user equipment cannot accurately reflect the current channel state, such as a scenario where the user equipment is in high-speed movement. This will bring negative effect to the performance of the close-loop CoMP transmission.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.